Ionization Gas Sensor Using Suspended Carbon Nanotube Beams

Abstract

An ionization sensor based on suspended carbon nanotubes (CNTs) was presented. A suspended CNT beam was fabricated by a low-temperature surface micromachining process using SU8 photoresist as the sacrificial layer. Application of a bias to the CNT beam generated very high non-linear electric fields near the tips of individual CNTs sufficient to ionize target gas molecules and initiate a breakdown current. The sensing mechanism of the CNT ionization sensor was discussed. The sensor response was tested in air, nitrogen, argon, and helium ambients. Each gas demonstrated a unique breakdown signature. Further, the sensor was tested with gaseous mixtures. The sensor exhibited good long-term stability and had comparable performance to other reported CNT-based ionization sensors in literature, which use high-temperature vapor deposition methods to grow CNTs. The sensor notably allowed for lower ionization voltages due to its reduced ionization gap size.

Crystalline-to-Amorphous Phase Transformation in CuO Nanowires for Gaseous Ionization and Sensing Application

“…In this work, the I – V curve of the initial air discharge plotted in Figure a clearly exhibits an upheaval in the emission current, which validates the discharge and further confirms the occurrence of ion bombardment toward the CuO NW cathode . The ions generated in air discharge, for example, charged oxygen species, are favorable to collide with the CuO lattice. , Meanwhile, the discharge current is also believed to provide Joule heating . Such a thermal effect will supplement the collision for amorphization, especially in the vicinity of nanotips with insufficient heat dissipation.…”

“…Many efforts have been made to prove that the gaseous ionization properties are dictated by the configuration of the discharge electrodes, especially the microstructure of surface. − In turn, the transport of the substance ( e.g. , ion) and energy toward the electrodes during ionization also tends to modify the solid-state microstructures.…”

“…26 The ions generated in air discharge, for example, charged oxygen species, are favorable to collide with the CuO lattice. 39,47 Meanwhile, the discharge current is also believed to provide Joule heating. 48 Such a thermal effect will supplement the collision for amorphization, especially in the vicinity of nanotips with insufficient heat dissipation.…”

Chemical selection for the calibration of general-purpose electronic noses based on Silhouette coefficients

“…This makes it difficult to objectively identify the drift mechanism and almost impossible to design appropriate strategies for correcting drift from unknown origins. Consequently, considering the compensation of drift, some researchers have concentrated on physical improvements on the gas sensor itself [13], [14], and others on algorithms [15]- [17]. Nevertheless, the drift mechanism is complex and inevitable, and so sensor drift has been identified as one of the primary obstacles to the mass production of E-noses [12].…”

Hybrid Platforms of Silicon Nanowires and Carbon Nanotubes in an Ionic Liquid Bucky Gel

“…For these reasons, SWCNTs are excellent conductors with physical properties of great importance for nanotechnology, electronics, optics, and other technological fields [ 16 , 29 , 30 , 31 ]. Furthermore, CNTs are also efficient absorbers able to trap light across the entire solar spectrum and therefore are considered strategic for future photovoltaic applications [ 32 , 33 ].…”